Explosive package



Sept. 19, 1967 D. s. PARTRIDGE 3,342,132

ExPLosIvE: PACKAGE: i

Filed April 13, 1966 AQUEOUS SLURRY AMMON|UM if :BAMMONIUMB NITRATEEXPLOSVE :'TRAT 1' DRY AMMONIUM NITRATE EXPLOSIVE AQUEOUS SLURRYAMMONIUMy NITRATE ExPLoswE WATER 'MPERV'OUS BARRIER 'TNVENTOR Dole S.Parrdge BY carl A. cnne AGENT United States Patent M 3,342,132 EXPLOSIVEPACKAGE Dale S. Partridge, Overland Park, Kans., assgnor to Gulf OilCorporation, Pittsburgh, Pa., a corporation of Penn- Sylvania liiiiedApr.. 13, 1966, Ser. No. 542,250 Claims. (Cl. 102-24) ABSTRACT 0F THEDISCLOSURE A combination of both shattering and heaving effect, as wellas more eilcient utilization of explosive force is obtained fro-m asubstantially cylindrical package of ammonium nitrate-based aqueousslurry explosive which surrounds a charge of dry ammoniumnitrate-carbonaceous fuel explosive sealed within a water-imperviousbarrier.

This invention relates to packaged blasting explosives. Moreparticularly, this invention is directed to an explosive package inwhich a water-sensitive explosive is contained in a seale-d imperviouscontainer inside a mass of water-insensitive explosive.

Blasting explosives comprising ammonium nitrate and a carbonaceous fuelwith or without sensitizers and auxiliary explosive additives are nowvery well known and widely used. The conventional ammonium nitrate-fueloil explosive compositions have very desirable properties, particularlywith regard to their ability to heave large masses of rock or earth.However, when blasting is done in vertical drill holes, it frequentlyhappens that water enters and collect-s in the hole. Ammoniumnitrate-fuel oil explosives are sensitive to the presence of water andwhen wet do `not give their usual performance. Therefore, it isnecessary that such explosives be kept dry. When these explosives aresealed in water-proof containers, the specic gravity of the container isusually less than that of water, and so it is diflicult to make theexplosive charge sink to the bottom of the hole. In coping with thissituation, a new type of water-insensitive explosive composition of highspecic gravity has been developed. This new class of explosives containsammonium nitrate, a solid fuel, auxiliary oxidizers and sensitizers,water, and a water-dispersible colloid which stabilizes the mixtureagainst settling of suspended solids. The new aqueous slurry explosiveshave become popular in hard rock mining where rather large verticaldrill holes are employed and entrance of water into the holes occursfrequently. The high specic gravity, water-insensitivity, and brisanceof the aqueous slurry explosives are very desirable. However, they aredifferent in character from the ammonium nitrate-fuel oil explosives.The desirability of using the two types of explosives together so as toobtain the combined advantages of both has become apparent. For example,a practice which has been used to some extent is the loading of aqueousslurry explosives in a bottom of a drill hole along with a suitablebooster and detonator and loading ammonium nitrate-fuel oil explosive ontop of the slurry explosive; then tiring the entire charge. Theresulting explosion is somewhat unbalanced in its effects, however, asmight 4be expected. It has been attempted to intersperse packages ofammonium nitrate-fuel oil explosive with aqueous slurry explosive in thedrill hole, but this has been found to be inconvenient and to givenonuniform results. Among other things which may occur in the blastingof such a charge are the shifting of explosive packages after they arein the hole and accidental puncturing of ammonium nitrate-fuel oilpackages during placement in the hole, permitting the explosive tobecome wet and less eifective.

I have found that the desirable features of the two types of explosivesmay be obtained conveniently and cheaply and with uniform results bymeans of a novel 3,342,l32 Patentedv Sept. 19, 1967 packagingarrangement. Preferably, my invention consists of a substantiallycylindrical package, in which a dry ammonium nitrate-carbonaceous fuelexplosive is sealed inside a water-proof barrier and is surrounded by amass of aqueous slurry explosive. The mass of aqueous slurry explosivemay be in semisolid gel form and, if so, can be handled in drums orother rigid containers. The gelled mass may be contained in plastic bagswhich are dumped out of the containers into the drill holes so that thecontainers may be re-used or, preferably, the gelled mass is put indurable cylindrical plastic containers both for shipping and placementin the drill hole, The package possesses substantial advantages amongwhich are the following: The water-proof bag of ammonium nitrate-fueloil explosive is protected from punctures and retained in a centrallylocated position by the flexible mass of aqueous gel which surrounds it.The specic gravity of the entire package is greater than water so thatthe package will readily sink to the bottom of the drill hole into whichwater has entered. The efficiency of the combination of explosives inthe package is greatly increased. This is believed to result frometlcient utilization of the high heat of detonation of the ammoniumnitrate-fuel oil explosive as a result of completely surrounding thisexplosive with the aqueous gel. The high velocity of the detonation ofthe aqueous gel explosive also appears to compensate for the normallylower velocity of the ammonium nitrate-carbonaceous fuel explosive. Themechanism by which improved results are obtained is probably not fullyunderstood. However, it has been demonstrated that packaging in thereverse arrangement with the gel on the inside does not give equivalentbehavior. It is therefore concluded that the benet results fromsurrounding the dry explosive with the gel and by separating the twoexplosives with a water-impervious barrier.

By reference to the drawing and the following illustrative example, thepractice of the invention will be clear to a person possessing skill inthe art. The drawing presents a cut-away view of a complete package(FIGURE l) as well as a cross-section of the same (FIGURE 2).

Example I mixture of ammonium nitrate with 6 weight percent fuel oil andthe open end was sealed. (See No. l in FIGURES 1 and 2.) The ammoniumnitrate employed in this explosive consisted of 50 percent whole prillsand 50 percent crushed prills so as to increase the bulk density,yielding an explosive composition with a specific gravity ofapproximately 1.0. The filled, impervious package of ammoniumnitrate-fuel oil explosive was placed inside an extruded polyethylenetube 7 inches in diameter and 25 pounds of aqueous slurry explosive insemisolid gel form was placed in the larger tube so that it completelysurrounded the smaller package of dry ammonium nitratefuel oil explosive(No. 3 in FIGURES l and 2). The external tube was then sealed forconvenience in handling.

The aqueous slurry composition contained 42 weight percent ammoniumnitrate, 14 weight percent sodium nitrate, 4 weight percenthexamethylenetetramine, about l5 weight percent coarse granularaluminum, about l weight percent paint grade aluminum flake, 23 weightpercent water and about 0.6 weight percent guar gum.

The explosive package was lowered into an S-inch diameter hole drilledvertically into Mesabi range taconite and was iired by means of anelectric cap and a l-pound pentolite booster placed in the bottom of thehole. The resulting explosion produced both the shattering of rockcustomarily observed with slurry explosive alone and at the same timealso heaved the mass of rock away from the face of the deposit,indicating that it posi sessed the gas-producing [and heaving abilitycharacteristic of the dry ammonium nitrate-fuel oil explosives.

The essential features of the improved explosive package are theprotection of the dry ammonium nitrate-fuel explosive from water and thesurrounding of this explosive with the aqueous gel explosive. This maybe accomplished in several ways. For example, individual arnmoniumnitrate prills may be impregnated with a hydrocarbon and coated torender them water-impervious, then mixed with he aqueous gel so thatthey become surrounded. Alternatively, small sealed plastic packages of-ammonium nitrate explosives may be produced, either individually orattached together in a manner similar to link sausages, and fed into thepackage at the same time as the slurry explosive. Preferably a containeris em- Y ployed which is designed with a centrally located waterproofinterior compartment which can be filled and sealed prior to placing the4surrounding charge of aqueous slurry explosive.

The dry ammonium nitrate-fuel oil explosive should be substantiallycompletely surrounded by the aqueous slurry, However, in a tall columnof explosive, the dry lammonium nitrate explosive may be surrounded withaqueous slurry on the sides but not at one or both ends, withsatisfactory results. In a charge of some length, however, with bothends covered only with the water-impervious barrier, less than afraction of one percent of the total exterior surface remains notsurrounded with aqueous gel. The surrounding of the charge is thussubstantially complete, so that detonation of the dry explosive underthe external pressure exerted by the high-velocity gel explosive isachieved.

In the above example, a charge consisting of half dry and half aqueousexplosive apparently accomplished both of the jobs normally done byeither of the two types of explosives in' about the same sine charge.This appears to indicate that some power is normally wasted in eitherthe rock shattering by the aqueous slurry or the heaving of mass by thedry explosive, and that the combination in the package utilizes thetotal power of both explosives to better advantage. Although the 50-50weight ratio of explosives in the package is not critical, approximatelyequal proportions are preferred for a product of general usefulness andversatility. In smaller drill holes of 5 to 7 inches in diameter ahigher proportion of the dry explosive, for example `as muchas 65percent, appears to be desirable. However, in larger Iholes of 9 inchesor more in diameter, the proportion of dry explosive may be varied overa broad range, permitting the characteristics of the combination to beadjusted to compensate for variations in behavior which are attributableto the size of the charge, and to adjust heaving ability so as to placethe dislodged rock at the desired distance from the face of the deposit.

The eiect obtained by the explosive package of this invention isessentially a pressure versus time curve of a type not previouslyobserved in ammonium nitrate explosives. As has been stated above, thisis believed to result from the detonation of a dry ammonium nitrateexplosive While surrounded by a previously initiated high velocityexplosion. The size of the internal package of dry ammonium nitrateexplosive does not appear to be of critical importance, as indicated bythe following example.

l Example II An explosive mixture was prepared by distributing 34 partsby weight of waterproof ammonium nitrate blasting prills made inaccordance with U.S. Patent 3,148,095 in an aqueous slurry mixturecontaining 15 parts of water, about 34 parts of water-soluble ammoniumnitrate, 2 parts of paint grade aluminum flake, 4 parts ofhexamethylenetetramine, 10 parts of sodium nitrate and about 0.5 partguar gum. The explosive mixture was packaged in plastic sausage casingsof various diameters and was tested. At a diameter of 3 inches onecharge failed to detonate, indicating that for small diameters, theexplosive should be formulated with greater sensitivity. At diameterslarger than 3 inches, the characteristic behavior of the improvedexplosive Ipackage was obtained with nofailures. These results indicateVthat the dry ammonium nitrate explosive may be employed in packages assmall as individual prills, if desired. Higher sensitivity requirementsare usually characteristic of small diameter changes of blastingexplosives. By employing a more sensitive slurry explosive, containinglarger proportions of such components as sensitizers, auxiliaryoxidizing agents and suspended solid fuel, this problem is readilyalleviated.r Sensitive explosives of the slurry type are available 'asarticles of commerce and suitable formulations have been published.

The use of watenproof blasting prills as the internal dry explosiveyields a readily pumpable explosive mass, so that the packagingprocedure may be carried out with greater ease and safety.

What is claimed is:

1. A substantially cylindrical package containing a dry explosivecomprising ammonium nit-rate and a oarbonaceous fuel, a Water-imperviousbarrier sealing said dry explosive and a rnass of aqueous slurryexplosive surrounding said dry explosive, said aqueous slurry explosivecomprising water, ammonium nitrate and suspended solid fuel.

2. A package according to claim 1 in which the waterimpervious barrieris a flexible plastic container.

3. A package according to claim 1 in which the Waterimfpervious barrieris la coating applied to the exterior surfaces `of individual ammoniumnitrate prills.

4. A .package according to claim 1 in which the diameter is less than 9inches and -more than 50 weight percent of the explosive therein is adry explosive comprising ammonium nitrate and a carbonaceous fuel.

5. A package according to claim 1 in which the diameter is at least 9inches and about 50 weight percent of the explosive therein is anaqueous slurry explosive cornprising water, ammonium nitrate andsuspended solid fuel.

References Cited UNITED STATES PATENTS 2,754,755 7/1956 Ruth et al102-24 2,892,406 `6/1959 Hradel et al. 102-23 3,046,887 7/ 1962Brinkley, et al. 102-22 3,046,888 7/1962 Gordon 102-22 BENJAMIN A.BORCHELT, Primary Examiner.

SAMUEL FEINBERG, Examiner.

V. R. PENDEGRASS, Assistant Examiner.

1. A SUBSTANTIALLY CYLINDRICAL PACKAGE CONTAINING A DRY EXPLOSIVECOMPRISING AMMONIUM NITRATE AND A CARBONACEOUS FUEL, A WATER-IMPERVIOUSBARRIER SEALING SAID